1. Field of the Invention
The present invention relates to an ink set and an inkjet recording method.
2. Description of the Related Art
In an inkjet recording apparatus, a pigment ink which uses a pigment since it has a feature of superior lightfastness and water resistance. However, in the inkjet recording apparatus which uses the pigment ink, ink discharge failure occurs due to clogging caused by the thickened ink by drying or foreign matter, and there is a problem that stable discharge is not possible. A pigment ink having a high pigment concentration, especially a black ink having a high pigment concentration, which supports high image density desired in recent years, is likely to be thickened by drying, and discharge failure becomes more significant.
Thus, for the purpose of improving discharge stability, an ink set for inkjet including a black ink using either carbon black dispersed in water without a dispersant or carbon black included in a polymer and an ink other than the black ink using a pigment included in a polymer is proposed (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2002-327138). However, with this proposed technology, there is a problem that discharge stability is not sufficient for a high pigment concentration.
Thus, to enable stable discharge for a high pigment concentration, an inkjet recording apparatus equipped with a printing maintenance and recovery unit is proposed (for example, see JP-A No. 2005-170035). The printing maintenance and recovery unit sucks an ink filled in a nozzle by a negative-pressure generating unit communicating with a cap sealing a nozzle surface such as suction pump and then wipes the nozzle surface with a wiping member composed of an elastic plate such as rubber. Thereby, air bubbles in a liquid chamber, a thickened ink, dust and so on are removed, and a stable state for ink discharge is maintained.
However, when viscous inks are being sucked using a common cap in a head including nozzle arrays for discharging different types of inks such as combination of a black ink of carbon black and pigment inks of other colors, only the thickened color pigment ink having a low viscosity compared to the black ink is sucked while the black ink cannot be sucked since the black ink of carbon black is likely to have a higher viscosity. Once non-discharge occurs, a problem occurs that the non-discharge cannot be recovered.
Accordingly, there is being asked at present to provide an ink set which provides a high image density and has superior discharge stability and discharge recovery.